156 Causes and Course of Organic Evolution 



compounds, or as dissociation products of albumins. Much 

 can be said in favor of both views, but, without entering into 

 this at present, it might shortly be said that leucin, iso-leucin, 

 aspartic acid, glutaminic acid, lysin, guanidin, arginin, phenyla- 

 lanin, tyro sin, and others of the amino-acid group are common 

 to plants and animals, though found only in definite genera, 

 or families, or even in certain tissues, and at definite periods 

 in the history of the individual organisms. 



The comparative study of proteins as found in plant and 

 animal cells has been so fully elaborated by Mann {57: 346-424) 

 that reference need only be made to his work. But as set 

 forth there, alike by Cohnheim and the author (pp. 349-352), 

 much difficulty is experienced in making accurate comparison 

 owing to the great variety and extreme complexity of the 

 albumin compounds. Mann further adds: "We may safely 

 assume that in their coarse chemical framework all groups of 

 plants and of animals agree, and that those characteristics 

 which are peculiar to each individual species are produced 

 by transformations and substitutions in 'side-chains'; and, 

 further, that this change is only possible by a new arrangement 

 of the different amino-acids both as regards the relative quan- 

 tities in which each acid is present and also the order in which 

 they are linked to one another." 



Ferments. The remarkable group that most physiologists 

 are inclining more and more to regard as protein compounds, 

 namely the ferments or ejizymes, are common in many cases 

 to the vegetable and animal kingdoms. These enzymes seem 

 at least in some cases to be formed in cells by transformation 

 of certain protein granules known as zymogens or ferment 

 producers. The longest known and best investigated of these 

 ferments is diastase. We know accurately that it is present 

 throughout the entire vegetable and animal scale, in order to 

 effect the chemical transformation of starch into sugar. Thus 

 amongst the Acaryota its secretion by various bacteria enables 

 them to liquefy and change starch into sugar, which is then 

 absorbed in nutrition. The yeast plant and many other fungi 

 form it, while algae like Spirogyra that produce abundant starch 

 change this by diastatic action. From the moss alliance up- 

 ward the relation of stored starch and of transforming diastase 

 seems invariable and intimate. Space considerations prevent 

 us doing more than to mention the two varieties, both of which 

 show well-marked peculiarities, and which may be called solu- 

 tion and corrosion diastase (69: 31). 



Diastase has been detected even in unicellular organisms 

 although from their structure it exists side by side with other 



